This disclosure relates to extrusion limiters for downhole oilfield tools. The extrusion limiters may typically be used in a fracturing plug, bridge plug, or packer, but may also be used in similar products that require contact or interaction with a cylindrical wall such as of well casing, pipe, etc. . . . .
Extrusion limiters typically include fins that are provided on a fracturing plug wedge or cone. The fins are delimited by straight, radial cuts. The number of fins created by these cuts can vary from two to as many as are necessary. A typical number of fins would be six to eight. During the setting of the fracturing plug, the fins break or bend outward and bridge the annulus between the mandrel of the fracturing plug and well casing or pipe. The fins help mitigate extrusion of an element made of rubber or equivalent material which is typically used for sealing against well casing.
A problem with extrusion limiters having fins delimited by straight cuts is that when the fins bend outward, the cuts may leave large gaps between the fins, and the gaps may allow some extrusion of the rubber. Although useful for most applications, extrusion limiters made with straight cuts may fail to provide adequate support to the rubber for limiting extrusion, especially when temperatures and/or pressures are high and rubber flows more easily through the gaps left between the fins. A common solution for improving support to the rubber is to include two sets of extrusion limiters with cuts that do not overlap each other. However, this solution requires additional components and leads to additional cost.
Thus, there is a continuing need in the art for extrusion limiters.